In the past decade, ALMA observations of protoplanetary disks revealed various substructures including gaps and rings. Their origin of substructures may be probed through statistical studies of their physical properties. We present the analyses of archival ALMA Band 6 continuum data of 43 disks (39 Class II and four Herbig Ae) in the Taurus–Auriga region. We employ a novel 2D super-resolution imaging technique based on sparse modeling to obtain images with high fidelity and spatial resolution. As a result, we have obtained images with spatial resolutions comparable to a few au (${0_{.}^{primeprime}02}$–${0_{.}^{primeprime}1}$), which is two to three times better than conventional CLEAN methods. All dust disks are spatially resolved, with the radii ranging from 8 to 238 au with a median radius of 45 au. Half of the disks harbor clear gap structures, the radial locations of which show a bimodal distribution with peaks at ≲20 au and ≳30 au. We also see structures indicating weak gaps at all the radii in the disk. We find that the widths of these gaps increase with their depths, which is consistent with the model of planet–disk interactions. The inferred planet mass–orbital radius distribution indicates that the planet distribution is analogous to our solar system. However, planets with Neptune mass or lower may exist in all the radii.
在过去十年中，ALMA 对原行星盘的观测揭示了包括间隙和环在内的各种亚结构。亚结构的起源可以通过对其物理特性的统计研究来探测。我们展示了对金牛座-Auriga 地区 43 个星盘（39 个 II 类和 4 个 Herbig Ae）的 ALMA Band 6 存档连续波数据的分析。我们采用了一种基于稀疏建模的新型二维超分辨率成像技术，以获得高保真和高空间分辨率的图像。因此，我们获得的图像空间分辨率相当于几au（${0_{.}^{primeprime}02}$-${0_{.}^{primeprime}1}$），是传统CLEAN方法的两到三倍。所有尘埃盘都是空间分辨的，半径从 8 到 238 au 不等，中位半径为 45 au。半数的尘埃盘具有明显的间隙结构，其径向位置呈双峰分布，峰值分别位于 ≲20 au 和 ≳30 au。我们还看到在磁盘的所有半径上都有显示弱间隙的结构。我们发现这些间隙的宽度随着深度的增加而增加，这与行星-圆盘相互作用模型是一致的。推断出的行星质量-轨道半径分布表明，行星分布与太阳系类似。然而，质量为海王星或更小的行星可能存在于所有半径中。
{"title":"ALMA 2D super-resolution imaging of Taurus–Auriga protoplanetary disks: Probing statistical properties of disk substructures","authors":"Masayuki Yamaguchi, Takayuki Muto, Takashi Tsukagoshi, Hideko Nomura, Naomi Hirano, Takeshi Nakazato, Shiro Ikeda, Motohide Tamura, Ryohei Kawabe","doi":"10.1093/pasj/psae022","DOIUrl":"https://doi.org/10.1093/pasj/psae022","url":null,"abstract":"In the past decade, ALMA observations of protoplanetary disks revealed various substructures including gaps and rings. Their origin of substructures may be probed through statistical studies of their physical properties. We present the analyses of archival ALMA Band 6 continuum data of 43 disks (39 Class II and four Herbig Ae) in the Taurus–Auriga region. We employ a novel 2D super-resolution imaging technique based on sparse modeling to obtain images with high fidelity and spatial resolution. As a result, we have obtained images with spatial resolutions comparable to a few au (${0_{.}^{primeprime}02}$–${0_{.}^{primeprime}1}$), which is two to three times better than conventional CLEAN methods. All dust disks are spatially resolved, with the radii ranging from 8 to 238 au with a median radius of 45 au. Half of the disks harbor clear gap structures, the radial locations of which show a bimodal distribution with peaks at ≲20 au and ≳30 au. We also see structures indicating weak gaps at all the radii in the disk. We find that the widths of these gaps increase with their depths, which is consistent with the model of planet–disk interactions. The inferred planet mass–orbital radius distribution indicates that the planet distribution is analogous to our solar system. However, planets with Neptune mass or lower may exist in all the radii.","PeriodicalId":20733,"journal":{"name":"Publications of the Astronomical Society of Japan","volume":"24 1","pages":""},"PeriodicalIF":2.3,"publicationDate":"2024-05-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141061354","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Broad Absorption Line Quasars (BALQSOs) represent a significant phenomenon in the realm of quasar astronomy, displaying distinct blueshifted broad absorption lines. These enigmatic objects serve as invaluable probes for unraveling the intricate structure and evolution of quasars, shedding light on the profound influence exerted by supermassive black holes on galaxy formation. The proliferation of large-scale spectroscopic surveys such as LAMOST (the Large Sky Area Multi-Object Fiber Spectroscopic Telescope), SDSS (the Sloan Digital Sky Survey), and DESI (the Dark Energy Spectroscopic Instrument) has exponentially expanded the repository of quasar spectra at our disposal. In this study, we present an innovative approach to streamline the identification of BALQSOs, leveraging the power of dimensionality reduction and machine-learning algorithms. Our dataset is meticulously curated from the SDSS Data Release 16 (DR16), amalgamating quasar spectra with classification labels sourced from the DR16Q quasar catalog. We employ a diverse array of dimensionality-reduction techniques, including principal component analysis (PCA), t-Distributed stochastic neighbor embedding (t-SNE), locally linear embedding (LLE), and isometric mapping (ISOMAP), to distill the essence of the original spectral data. The resultant low-dimensional representations serve as inputs for a suite of machine-learning classifiers, including the robust XGBoost and Random Forest models. Through rigorous experimentation, we unveil PCA as the most effective dimensionality-reduction methodology, adeptly navigating the intricate balance between dimensionality reduction and preservation of vital spectral information. Notably, the synergistic fusion of PCA with the XGBoost classifier emerges as the pinnacle of efficacy in the BALQSO classification endeavor, boasting impressive accuracy rates of $97.60%$ by 10-cross validation and $96.92%$ on the outer test sample. This study not only introduces a novel machine-learning-based paradigm for quasar classification but also offers invaluable insights transferrable to a myriad of spectral classification challenges pervasive in the realm of astronomy.
{"title":"Efficient identification of broad absorption line quasars using dimensionality reduction and machine learning","authors":"Wei-Bo Kao, Yanxia Zhang, Xue-Bing Wu","doi":"10.1093/pasj/psae037","DOIUrl":"https://doi.org/10.1093/pasj/psae037","url":null,"abstract":"Broad Absorption Line Quasars (BALQSOs) represent a significant phenomenon in the realm of quasar astronomy, displaying distinct blueshifted broad absorption lines. These enigmatic objects serve as invaluable probes for unraveling the intricate structure and evolution of quasars, shedding light on the profound influence exerted by supermassive black holes on galaxy formation. The proliferation of large-scale spectroscopic surveys such as LAMOST (the Large Sky Area Multi-Object Fiber Spectroscopic Telescope), SDSS (the Sloan Digital Sky Survey), and DESI (the Dark Energy Spectroscopic Instrument) has exponentially expanded the repository of quasar spectra at our disposal. In this study, we present an innovative approach to streamline the identification of BALQSOs, leveraging the power of dimensionality reduction and machine-learning algorithms. Our dataset is meticulously curated from the SDSS Data Release 16 (DR16), amalgamating quasar spectra with classification labels sourced from the DR16Q quasar catalog. We employ a diverse array of dimensionality-reduction techniques, including principal component analysis (PCA), t-Distributed stochastic neighbor embedding (t-SNE), locally linear embedding (LLE), and isometric mapping (ISOMAP), to distill the essence of the original spectral data. The resultant low-dimensional representations serve as inputs for a suite of machine-learning classifiers, including the robust XGBoost and Random Forest models. Through rigorous experimentation, we unveil PCA as the most effective dimensionality-reduction methodology, adeptly navigating the intricate balance between dimensionality reduction and preservation of vital spectral information. Notably, the synergistic fusion of PCA with the XGBoost classifier emerges as the pinnacle of efficacy in the BALQSO classification endeavor, boasting impressive accuracy rates of $97.60%$ by 10-cross validation and $96.92%$ on the outer test sample. This study not only introduces a novel machine-learning-based paradigm for quasar classification but also offers invaluable insights transferrable to a myriad of spectral classification challenges pervasive in the realm of astronomy.","PeriodicalId":20733,"journal":{"name":"Publications of the Astronomical Society of Japan","volume":"46 1","pages":""},"PeriodicalIF":2.3,"publicationDate":"2024-05-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141061359","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
We present time-dependent nova outburst models with optically thick winds for 1.2 and 1.35$, M_{odot }$ white dwarfs (WDs) with a mass-accretion rate of $5 times 10^{-9}, M_{odot }$ yr−1 and for a 1.3$, M_{odot }$ WD with $2 times 10^{-9}, M_{odot }$ yr−1. The X-ray flash occurs 11 d before the optical peak of the 1.2$, M_{odot }$ WD and 2.5 d before the peak of the 1.3$, M_{odot }$ WD. The wind mass-loss rate of the 1.2$, M_{odot }$ WD (1.3$, M_{odot }$ WD) reaches a peak of $6.4 times 10^{-5}, M_{odot }$ yr−1 ($7.4 times 10^{-5}, M_{odot }$ yr−1) at the epoch of the maximum photospheric expansion with the lowest photospheric temperature of log Tph (K) = 4.33 (4.35). The nuclear energy generated during the outburst is lost in the form of radiation (61% for the 1.2$, M_{odot }$ WD; 47% for the 1.3$, M_{odot }$ WD), gravitational energy of ejecta (39%; 52%), and kinetic energy of the wind (0.28%; 0.29%). We found an empirical relation for fast novae between the time to optical maximum from the outburst tpeak and the expansion timescale τexp. With this relation, we are able to predict the time to optical maximum tpeak from the ignition model (at t = 0) without following a time-consuming nova wind evolution.
{"title":"Physics of nova outbursts: Theoretical models of classical nova outbursts with optically thick winds on 1.2 M⊙ and 1.3 M⊙ white dwarfs","authors":"Mariko Kato, Hideyuki Saio, Izumi Hachisu","doi":"10.1093/pasj/psae038","DOIUrl":"https://doi.org/10.1093/pasj/psae038","url":null,"abstract":"We present time-dependent nova outburst models with optically thick winds for 1.2 and 1.35$, M_{odot }$ white dwarfs (WDs) with a mass-accretion rate of $5 times 10^{-9}, M_{odot }$ yr−1 and for a 1.3$, M_{odot }$ WD with $2 times 10^{-9}, M_{odot }$ yr−1. The X-ray flash occurs 11 d before the optical peak of the 1.2$, M_{odot }$ WD and 2.5 d before the peak of the 1.3$, M_{odot }$ WD. The wind mass-loss rate of the 1.2$, M_{odot }$ WD (1.3$, M_{odot }$ WD) reaches a peak of $6.4 times 10^{-5}, M_{odot }$ yr−1 ($7.4 times 10^{-5}, M_{odot }$ yr−1) at the epoch of the maximum photospheric expansion with the lowest photospheric temperature of log Tph (K) = 4.33 (4.35). The nuclear energy generated during the outburst is lost in the form of radiation (61% for the 1.2$, M_{odot }$ WD; 47% for the 1.3$, M_{odot }$ WD), gravitational energy of ejecta (39%; 52%), and kinetic energy of the wind (0.28%; 0.29%). We found an empirical relation for fast novae between the time to optical maximum from the outburst tpeak and the expansion timescale τexp. With this relation, we are able to predict the time to optical maximum tpeak from the ignition model (at t = 0) without following a time-consuming nova wind evolution.","PeriodicalId":20733,"journal":{"name":"Publications of the Astronomical Society of Japan","volume":"129 1","pages":""},"PeriodicalIF":2.3,"publicationDate":"2024-05-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140933920","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Large ground-based solar telescopes are equipped with adaptive optics systems to correct wavefront distortions induced in the turbulent atmosphere. The design of the adaptive optics system strongly depends on the vertical profiles of the optical turbulence. In particular, the characteristics of the optical turbulence determine the design of tomographic adaptive optics systems, which provide image correction within a wide field of view. In the article, a new method to estimate reference optical turbulence characteristics from Era-5 reanalysis assimilated data is presented. This method is based on the dependence of the air refractive index structure constant $C_n^2$ on the vertical shears of wind speed as well as the outer scale of turbulence L0. The L0 parameter is estimated by minimization of the dispersion between the modeled and measured values of the refractive index structure constant $C_n^2$ within the surface layer. For the first time, parametrization coefficients and reference profiles of optical turbulence averaged for the period 1940–2022 are calculated for the Large Solar Vacuum Telescope (LSVT) site. The calculated optical turbulence profiles are representative; these profiles correspond to typical changes of the measured values of the Fried parameter, the isoplanatic angle, and the outer scale of turbulence at the LSVT site. The model turbulence profiles are verified taking into account the Shack–Hartmann wavefront sensor measurements at the LSVT. The higher accuracy of estimation of the optical turbulence characteristics makes it possible to refine parameters relevant to the LSVT adaptive optics system. The obtained results can be used in order to develop high-resolution solar adaptive optics technologies as applied to ground-based telescopes including those using the principles of atmospheric tomography.
{"title":"Reference optical turbulence characteristics at the Large Solar Vacuum Telescope site","authors":"Artem Yu Shikhovtsev","doi":"10.1093/pasj/psae031","DOIUrl":"https://doi.org/10.1093/pasj/psae031","url":null,"abstract":"Large ground-based solar telescopes are equipped with adaptive optics systems to correct wavefront distortions induced in the turbulent atmosphere. The design of the adaptive optics system strongly depends on the vertical profiles of the optical turbulence. In particular, the characteristics of the optical turbulence determine the design of tomographic adaptive optics systems, which provide image correction within a wide field of view. In the article, a new method to estimate reference optical turbulence characteristics from Era-5 reanalysis assimilated data is presented. This method is based on the dependence of the air refractive index structure constant $C_n^2$ on the vertical shears of wind speed as well as the outer scale of turbulence L0. The L0 parameter is estimated by minimization of the dispersion between the modeled and measured values of the refractive index structure constant $C_n^2$ within the surface layer. For the first time, parametrization coefficients and reference profiles of optical turbulence averaged for the period 1940–2022 are calculated for the Large Solar Vacuum Telescope (LSVT) site. The calculated optical turbulence profiles are representative; these profiles correspond to typical changes of the measured values of the Fried parameter, the isoplanatic angle, and the outer scale of turbulence at the LSVT site. The model turbulence profiles are verified taking into account the Shack–Hartmann wavefront sensor measurements at the LSVT. The higher accuracy of estimation of the optical turbulence characteristics makes it possible to refine parameters relevant to the LSVT adaptive optics system. The obtained results can be used in order to develop high-resolution solar adaptive optics technologies as applied to ground-based telescopes including those using the principles of atmospheric tomography.","PeriodicalId":20733,"journal":{"name":"Publications of the Astronomical Society of Japan","volume":"36 1","pages":""},"PeriodicalIF":2.3,"publicationDate":"2024-05-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140934242","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
An emission line at ∼6.7 keV is attributable to an He-like iron K-shell transition, which indicates existence of a thin thermal plasma with a temperature of several keV. Using Suzaku archival data, we searched for the iron K-line from the spiral galaxy NGC 6946, and found it at 6.68 ± 0.07 keV at the 3.1σ level in the central $rle {2.^{prime }5}$ region. The iron line luminosity from the central region was estimated to be (2.3 ± 1.2) × 1037 erg s−1 at a distance of 5.5 Mpc. The origin of the iron emission line is discussed.
{"title":"Suzaku observation of an iron K-shell line in the spiral galaxy NGC 6946","authors":"Shigeo Yamauchi, Azusa Inaba, Yumiko Anraku","doi":"10.1093/pasj/psae028","DOIUrl":"https://doi.org/10.1093/pasj/psae028","url":null,"abstract":"An emission line at ∼6.7 keV is attributable to an He-like iron K-shell transition, which indicates existence of a thin thermal plasma with a temperature of several keV. Using Suzaku archival data, we searched for the iron K-line from the spiral galaxy NGC 6946, and found it at 6.68 ± 0.07 keV at the 3.1σ level in the central $rle {2.^{prime }5}$ region. The iron line luminosity from the central region was estimated to be (2.3 ± 1.2) × 1037 erg s−1 at a distance of 5.5 Mpc. The origin of the iron emission line is discussed.","PeriodicalId":20733,"journal":{"name":"Publications of the Astronomical Society of Japan","volume":"36 1","pages":""},"PeriodicalIF":2.3,"publicationDate":"2024-05-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140933938","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Paul K H Yeung, Shiu-Hang Lee, Tsunefumi Mizuno, Aya Bamba
Based on the 13.7 yr Fermi-LAT data, Yeung, Bamba, and Sano (2023, PASJ, 75, 384) claimed detection of two γ-ray sources (namely Src-NE and Src-NW) associated with the supernova remnant (SNR) G298.6−0.0, and interpreted it as an old GeV SNR interacting with molecular clouds (MCs). In this follow-up study, we refine the flux measurements below 2 GeV with Fermi-LAT event types of better angular reconstruction. Then, we report our γ-ray spectral fittings and cosmic-ray phenomenology in a hadronic scenario, considering both the shell and MC regions of SNR G298.6−0.0. We confirm that the γ-ray spectra of both Src-NE and Src-NW exhibit spectral breaks, at $1.50_{-0.50}^{+0.60}$ and $0.68_{-0.11}^{+0.32}:$GeV, respectively. Src-NW has a harder broad-band photon index than Src-NE, suggesting an appreciable difference between the physical separations of their respective emission sites from SNR G298.6−0.0. The cosmic-ray spectrum responsible for Src-NE starts with a minimum energy $E_mathrm{CR,min}=1.38_{-0.16}^{+0.47}:$GeV, and has a proton index $Gamma _mathrm{CR}=2.57_{-0.21}^{+0.18}$ below the exponential cutoff energy $E_mathrm{CR,max}=240_{-150}^{+240}:$GeV. Accordingly, we argue that Src-NE is dominated by the SNR shell, while only a minor portion of lower-energy emission is contributed by the MCs interacting with the SNR. The cosmic-ray population for Src-NW starts at a higher energy such that the ECR, min ratio of Src-NW to Src-NE is ≳2. The high ECR, min, as well as the high cosmic-ray energy density required (∼26 eV cm−3), supports the interpretation that Src-NW is predominantly the γ-ray emission from the farther MCs being bombarded by protons that had earlier escaped from SNR G298.6−0.0. By comparing the high-energy features of G298.6−0.0 with those of analogical SNRs, especially SNR W 28 and SNR W 44, we further constrain the age of SNR G298.6−0.0 to be 10–30 kyr, under the assumption of a purely hadronic scenario.
基于13.7年的费米-LAT数据，Yeung、Bamba和Sano（2023，PASJ，75，384）声称探测到了两个与超新星残余（SNR）G298.6-0.0相关的γ射线源（即Src-NE和Src-NW），并将其解释为一个与分子云（MC）相互作用的旧GeV SNR。在这项后续研究中，我们利用费米-LAT事件类型改进了2 GeV以下的通量测量，以获得更好的角度重建。然后，我们报告了在强子情景下的γ射线光谱拟合和宇宙射线现象学，同时考虑了SNR G298.6-0.0的壳区和MC区。我们证实Src-NE和Src-NW的γ射线谱线都表现出谱线断裂，分别为$1.50_{-0.50}^{+0.60}$和$0.68_{-0.11}^{+0.32}:$GeV。Src-NW的宽带光子指数比Src-NE要高，这表明它们各自的发射场与SNR G298.6-0.0的物理距离有明显的不同。Src-NE的宇宙射线频谱从最低能量$E_mathrm{CR,min}=1.38_{-0.16}^{+0.47}/:$GeV开始，质子指数$Gamma _mathrm{CR}=2.57_{-0.21}^{+0.18}$低于指数截止能量$E_mathrm{CR,max}=240_{-150}^{+240}/:$GeV。因此，我们认为Src-NE是由SNR外壳主导的，而与SNR相互作用的MC只贡献了一小部分低能发射。Src-NW的宇宙射线群开始于较高的能量，因此Src-NW与Src-NE的ECR，min比值为≳2。高ECR，min和所需的高宇宙射线能量密度（∼26 eV cm-3）支持这样的解释，即Src-NW主要是来自较远的MC的γ射线发射，这些MC受到了早先从SNR G298.6-0.0逃逸出来的质子的轰击。通过将 G298.6-0.0 的高能特征与同类 SNR（尤其是 SNR W 28 和 SNR W 44）的高能特征进行比较，我们进一步推测 SNR G298.6-0.0 的年龄为 10-30 kyr（假设为纯强子情况）。
{"title":"Examining a hadronic γ-ray scenario for the radiative shell and molecular clouds of the old GeV supernova remnant G298.6−0.0","authors":"Paul K H Yeung, Shiu-Hang Lee, Tsunefumi Mizuno, Aya Bamba","doi":"10.1093/pasj/psae025","DOIUrl":"https://doi.org/10.1093/pasj/psae025","url":null,"abstract":"Based on the 13.7 yr Fermi-LAT data, Yeung, Bamba, and Sano (2023, PASJ, 75, 384) claimed detection of two γ-ray sources (namely Src-NE and Src-NW) associated with the supernova remnant (SNR) G298.6−0.0, and interpreted it as an old GeV SNR interacting with molecular clouds (MCs). In this follow-up study, we refine the flux measurements below 2 GeV with Fermi-LAT event types of better angular reconstruction. Then, we report our γ-ray spectral fittings and cosmic-ray phenomenology in a hadronic scenario, considering both the shell and MC regions of SNR G298.6−0.0. We confirm that the γ-ray spectra of both Src-NE and Src-NW exhibit spectral breaks, at $1.50_{-0.50}^{+0.60}$ and $0.68_{-0.11}^{+0.32}:$GeV, respectively. Src-NW has a harder broad-band photon index than Src-NE, suggesting an appreciable difference between the physical separations of their respective emission sites from SNR G298.6−0.0. The cosmic-ray spectrum responsible for Src-NE starts with a minimum energy $E_mathrm{CR,min}=1.38_{-0.16}^{+0.47}:$GeV, and has a proton index $Gamma _mathrm{CR}=2.57_{-0.21}^{+0.18}$ below the exponential cutoff energy $E_mathrm{CR,max}=240_{-150}^{+240}:$GeV. Accordingly, we argue that Src-NE is dominated by the SNR shell, while only a minor portion of lower-energy emission is contributed by the MCs interacting with the SNR. The cosmic-ray population for Src-NW starts at a higher energy such that the ECR, min ratio of Src-NW to Src-NE is ≳2. The high ECR, min, as well as the high cosmic-ray energy density required (∼26 eV cm−3), supports the interpretation that Src-NW is predominantly the γ-ray emission from the farther MCs being bombarded by protons that had earlier escaped from SNR G298.6−0.0. By comparing the high-energy features of G298.6−0.0 with those of analogical SNRs, especially SNR W 28 and SNR W 44, we further constrain the age of SNR G298.6−0.0 to be 10–30 kyr, under the assumption of a purely hadronic scenario.","PeriodicalId":20733,"journal":{"name":"Publications of the Astronomical Society of Japan","volume":"11 1","pages":""},"PeriodicalIF":2.3,"publicationDate":"2024-05-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140829840","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
One of the promising mechanisms to explain the stable jet speed of SS 433 is the magic speed, which is established by the balance between radiation pressure and radiation drag (and gravity). We examine the magic speed in the optically thick sub-relativistic flows for several typical situations, such as plane-parallel and spherical cases, and show that it is difficult to establish the magic speed in the simple optically thick flows in contrast to the optically thin ones. Instead, we propose the funnel jets as an improved model. That is, we consider the optically thick flows in the funnel, which is formed by the supercritical accretion disk, and mass and radiation energy are injected from the funnel wall. In this model the mass-accretion rate determines the configuration of the funnel, the increasing mass-loss rate of jets, the radiative environments, and then the sub-relativistic magic speed is naturally established.
神奇速度是解释 SS 433 稳定喷流速度的可行机制之一，它由辐射压力和辐射阻力（以及重力）之间的平衡决定。我们研究了几种典型情况（如平面平行和球面情况）下光厚亚相对论流的神奇速度，结果表明，与光薄流相比较，在简单的光厚流中很难建立神奇速度。相反，我们提出了漏斗喷流作为改进模型。也就是说，我们考虑的是由超临界吸积盘形成的漏斗中的光学厚流，质量和辐射能量从漏斗壁注入。在这个模型中，质量增殖速度决定了漏斗的构造、喷流质量损失率的增加和辐射环境，然后亚相对论魔速就自然而然地建立起来了。
{"title":"Magic speed under radiation drag for the optically thick outflows and SS 433 jets","authors":"Jun Fukue","doi":"10.1093/pasj/psae030","DOIUrl":"https://doi.org/10.1093/pasj/psae030","url":null,"abstract":"One of the promising mechanisms to explain the stable jet speed of SS 433 is the magic speed, which is established by the balance between radiation pressure and radiation drag (and gravity). We examine the magic speed in the optically thick sub-relativistic flows for several typical situations, such as plane-parallel and spherical cases, and show that it is difficult to establish the magic speed in the simple optically thick flows in contrast to the optically thin ones. Instead, we propose the funnel jets as an improved model. That is, we consider the optically thick flows in the funnel, which is formed by the supercritical accretion disk, and mass and radiation energy are injected from the funnel wall. In this model the mass-accretion rate determines the configuration of the funnel, the increasing mass-loss rate of jets, the radiative environments, and then the sub-relativistic magic speed is naturally established.","PeriodicalId":20733,"journal":{"name":"Publications of the Astronomical Society of Japan","volume":"29 1","pages":""},"PeriodicalIF":2.3,"publicationDate":"2024-05-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140829731","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
We investigate a mechanism to form and keep a planar spatial distribution of satellite galaxies in the Milky Way (MW), which is called the satellite plane. It has been pointed out that the ΛCDM cosmological model hardly explains the existence of such a satellite plane, so it is regarded as one of the serious problems in the current cosmology. We here focus on a rotation of the gravitational potential of a host galaxy, i.e., a so-called figure rotation, following the previous suggestion that this effect can induce the tilt of a so-called tube orbit. Our calculation shows that a figure rotation of a triaxial potential forms a stable orbital plane perpendicular to the rotational axis of the potential. Thus, it is suggested that the MW’s dark halo is rotating with its axis being around the normal line of the satellite plane. Additionally, we find that a small velocity dispersion of satellites is required to keep the flatness of the planar structure, namely the standard derivation of their velocities perpendicular to the satellite plane needs to be smaller than their mean rotational velocity on the plane. Although not all the MW’s satellites satisfy this condition, a fraction of them, called member satellites, which are prominently on the plane, do satisfy it. We suggest that this picture explaining the observed satellite plane can be achieved by the filamentary accretion of dark matter associated with the formation of the MW and a group infall of member satellites along this cosmic filament.
{"title":"New insights on the dynamics of satellite galaxies: Effects of the figure rotation of a host galaxy","authors":"Genta Sato, Masashi Chiba","doi":"10.1093/pasj/psae026","DOIUrl":"https://doi.org/10.1093/pasj/psae026","url":null,"abstract":"We investigate a mechanism to form and keep a planar spatial distribution of satellite galaxies in the Milky Way (MW), which is called the satellite plane. It has been pointed out that the ΛCDM cosmological model hardly explains the existence of such a satellite plane, so it is regarded as one of the serious problems in the current cosmology. We here focus on a rotation of the gravitational potential of a host galaxy, i.e., a so-called figure rotation, following the previous suggestion that this effect can induce the tilt of a so-called tube orbit. Our calculation shows that a figure rotation of a triaxial potential forms a stable orbital plane perpendicular to the rotational axis of the potential. Thus, it is suggested that the MW’s dark halo is rotating with its axis being around the normal line of the satellite plane. Additionally, we find that a small velocity dispersion of satellites is required to keep the flatness of the planar structure, namely the standard derivation of their velocities perpendicular to the satellite plane needs to be smaller than their mean rotational velocity on the plane. Although not all the MW’s satellites satisfy this condition, a fraction of them, called member satellites, which are prominently on the plane, do satisfy it. We suggest that this picture explaining the observed satellite plane can be achieved by the filamentary accretion of dark matter associated with the formation of the MW and a group infall of member satellites along this cosmic filament.","PeriodicalId":20733,"journal":{"name":"Publications of the Astronomical Society of Japan","volume":"73 1","pages":""},"PeriodicalIF":2.3,"publicationDate":"2024-04-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140802619","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Radiation hydrodynamical equations with Compton scattering are generally difficult to solve analytically, and usually examined numerically, even if in the subrelativistic regime. We examine the equations available in the subrelativistic regime of kBT$/$(mec2) ≲ 0.1, hν$/$(mec2) ≲ 0.1, and v$/$c ≲ 0.1, where T is the electron temperature, ν the photon frequency, and v the fluid bulk velocity. For simplicity, we ignore the induced scattering terms. We then seek and obtain analytical solutions of frequency-dependent radiative moment equations of a hot plasma with bulk motions for several situations in the subrelativistic regime. For example, in the static case of a plane-parallel atmosphere without bulk motions, where equations involve the generalized Kompaneets equation with subrelativistic corrections, we find the Wien-type solution, which reduces to the usual Milne–Eddington solution in the nonrelativistic limit, as well as the power-law-type one, which has a form of [hν$/$(kBT)]−4. In the moving case of an accelerating one-dimensional flow with bulk motions, we also find the Wien-type and the power-law-type solutions affected by the bulk Compton effect. Particularly, in the Wien-type solutions, due to the bulk Compton effect, the radiation fields gain momentum from the hot plasma in the low-frequency regime of hν < 3kBT, while they lose it in the high-frequency regime of hν > 3kBT.
{"title":"Radiation hydrodynamics in a moving plasma with Compton scattering: Frequency-dependent solutions","authors":"Jun Fukue","doi":"10.1093/pasj/psae024","DOIUrl":"https://doi.org/10.1093/pasj/psae024","url":null,"abstract":"Radiation hydrodynamical equations with Compton scattering are generally difficult to solve analytically, and usually examined numerically, even if in the subrelativistic regime. We examine the equations available in the subrelativistic regime of kBT$/$(mec2) ≲ 0.1, hν$/$(mec2) ≲ 0.1, and v$/$c ≲ 0.1, where T is the electron temperature, ν the photon frequency, and v the fluid bulk velocity. For simplicity, we ignore the induced scattering terms. We then seek and obtain analytical solutions of frequency-dependent radiative moment equations of a hot plasma with bulk motions for several situations in the subrelativistic regime. For example, in the static case of a plane-parallel atmosphere without bulk motions, where equations involve the generalized Kompaneets equation with subrelativistic corrections, we find the Wien-type solution, which reduces to the usual Milne–Eddington solution in the nonrelativistic limit, as well as the power-law-type one, which has a form of [hν$/$(kBT)]−4. In the moving case of an accelerating one-dimensional flow with bulk motions, we also find the Wien-type and the power-law-type solutions affected by the bulk Compton effect. Particularly, in the Wien-type solutions, due to the bulk Compton effect, the radiation fields gain momentum from the hot plasma in the low-frequency regime of hν &lt; 3kBT, while they lose it in the high-frequency regime of hν &gt; 3kBT.","PeriodicalId":20733,"journal":{"name":"Publications of the Astronomical Society of Japan","volume":"16 1","pages":""},"PeriodicalIF":2.3,"publicationDate":"2024-04-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140576287","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Results of the long-term monitoring observations by the Hitachi 32 m radio telescope of the 6.7 GHz Class II methanol masers associated with four high-mass star-forming regions are presented. We detected periodic flux variability in G06.795−0.257, G10.472+0.027, G12.209−0.102, and G13.657−0.599 with the periods of 968, 1624, 1272, and 1266 d, respectively, although the detected period is tentative due to the short monitoring term relative to the estimated period. The facts that the flux variation patterns show the symmetric sine curves and that the luminosities of the central protostar and periods of maser flux variation are consistent with the expected period–luminosity (PL) relation suggest that the mechanisms of maser flux variability of G10.472+0.027 and G12.209−0.102 can be explained by protostellar pulsation instability. From the PL relation, the central stars of these two sources are expected to be very high-mass protostars with a mass of $sim 40, M_{odot }$ and to have a mass accretion rate of $sim 2 times 10^{-2}, M_{odot }:$yr−1. On the other hand, G06.795−0.257 and G13.657−0.599 have intermittent variation patterns and have luminosities that are an order of magnitude smaller than those expected from the PL relation, suggesting that the variation mechanisms of these sources originated from a binary system. Since almost all the maser features vary with the same period regardless of the geometry, periodic accretion models may be appropriate mechanisms for flux variability in G06.795−0.257 and G13.657−0.599.
{"title":"The candidates of long-periodic variable sources in 6.7 GHz methanol masers associated with four high-mass star-forming regions","authors":"Yoshihiro Tanabe, Yoshinori Yonekura","doi":"10.1093/pasj/psae021","DOIUrl":"https://doi.org/10.1093/pasj/psae021","url":null,"abstract":"Results of the long-term monitoring observations by the Hitachi 32 m radio telescope of the 6.7 GHz Class II methanol masers associated with four high-mass star-forming regions are presented. We detected periodic flux variability in G06.795−0.257, G10.472+0.027, G12.209−0.102, and G13.657−0.599 with the periods of 968, 1624, 1272, and 1266 d, respectively, although the detected period is tentative due to the short monitoring term relative to the estimated period. The facts that the flux variation patterns show the symmetric sine curves and that the luminosities of the central protostar and periods of maser flux variation are consistent with the expected period–luminosity (PL) relation suggest that the mechanisms of maser flux variability of G10.472+0.027 and G12.209−0.102 can be explained by protostellar pulsation instability. From the PL relation, the central stars of these two sources are expected to be very high-mass protostars with a mass of $sim 40, M_{odot }$ and to have a mass accretion rate of $sim 2 times 10^{-2}, M_{odot }:$yr−1. On the other hand, G06.795−0.257 and G13.657−0.599 have intermittent variation patterns and have luminosities that are an order of magnitude smaller than those expected from the PL relation, suggesting that the variation mechanisms of these sources originated from a binary system. Since almost all the maser features vary with the same period regardless of the geometry, periodic accretion models may be appropriate mechanisms for flux variability in G06.795−0.257 and G13.657−0.599.","PeriodicalId":20733,"journal":{"name":"Publications of the Astronomical Society of Japan","volume":"8 1","pages":""},"PeriodicalIF":2.3,"publicationDate":"2024-04-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140575906","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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